Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session M6: Ballistics II: Experiments and Phenomenology |
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Chair: Lawrence Hull, Los Alamos National Laboratory Room: Grand Ballroom VI |
Wednesday, June 29, 2011 11:00AM - 11:15AM |
M6.00001: Proton Radiography of Shape Charge Jets Penetrating Teflon and Explosive Eric N. Ferm, Michael W. Burkett, Larry M. Hull, Mark Marr-Lyon, Wendy V. McNeil, Chris L. Morris, Paul M. Rightley We have used proton radiography at the Los Alamos Neutron Science Center to observe viper shaped charge jets penetrating inert and explosive materials. A viper jet was observed penetrating both Teflon and PBX 9501. Radiographs captured the penetration events at several times and are analyzed to determine the density of the materials imaged at each time. The interfaces and shock waves in the flow are clearly evident in the images. Multiple time images allow the determination of the velocities of the interfaces and shock waves. Comparisons are made in the Teflon case with estimates of penetration rates and densities using the quasi-steady approximation analysis used in many terminal ballistics models. The PBX 9501 clearly detonated from the impact of the shape charge jet tip traveling at 9.1 mm/s. The detonation wave is examined to see what support it obtains from the pursing jet and the jet is examined to find the influence of the explosive products on penetration velocity. This experiment gives us experimental results of in-situ penetration process that can be used to verify common modeling techniques and fluid mechanic calculations of the penetration process. [Preview Abstract] |
Wednesday, June 29, 2011 11:15AM - 11:30AM |
M6.00002: Mechanism of Anomalous Penetration of Shaped Charge Jet into Ceramics Boris Rumyantsev, Vladimir Klimenko Our experiment [1] shows anomalous penetration of SCJ into ceramics, namely, at some moment penetration is temporarily stopped and then continue to move. To study mechanism of this complex process we used numerical simulation by 2D-hydrocode. As a result, we have found process that plays key role in penetration braking. Jet tip destroys ceramics. Small fragments move radially to axis and blockade jet motion [2]. Intense interaction of the jet with ceramics fragments leads to dispersion, heating, melting and evaporation of jet. Leading part of the jet turns into gas and penetration is stopped. But, back part of the jet remains in solid state and continues motion. After some delay it arrives to bottom of cavern and continues penetration process. \\[4pt] [1] B. V. Rumyantsev, Penetration Kinetics of Cumulative Jet into Brittle Materials, ISSN 1063-7842, Technical Physics, 2009, Vol. 54, No. 6, pp. 790-794.\\[0pt] [2] B.V. Rumyantsev, V.Yu. Klimenko, Study of Mechanism of Penetration of Shape Charge Jet into Ceramic Armor, Inter. Conference on Shock Waves in Condensed Matter, St.Petersburg - Novgorod, Russia, 2010, pp. 210-215. [Preview Abstract] |
Wednesday, June 29, 2011 11:30AM - 11:45AM |
M6.00003: X-Ray Tomography to Measure Size of Fragments from Penetration of High-Velocity Tungsten Rods Zach Stone, Romy Hanna, Stephan Bless, Scott Levinson Behind-armor debris that results from tungsten rods penetrating armor steel at 2 km/s was studied by analysis of recovered fragments. Fragment recovery was by means of particleboard. Individual fragments were analyzed by x-ray tomography, which provides information for fragment identification, mass, shape, and penetration down to masses of a few milligrams. The experiments were complemented by AUTODYN SPH calculations to provide the exit velocity and the strain rate at the time of particle formation. There were four types of fragments: steel or tungsten, and generated from the channel or from the breakout through the target rear surface. Channel fragment motions were well described by Tate theory. Breakout fragments had velocities from the projectile remnant to the channel velocity, apparently depending on where in the projectile a fragment originated. The fragment size distribution was extremely broad and did not correlate well with simple uniform-fragment-size models, e.g., Grady Kipp [Preview Abstract] |
Wednesday, June 29, 2011 11:45AM - 12:00PM |
M6.00004: Numerical Study on the High-Speed Water-Entry of Hemispherical and Ogival Projectiles Zitao Guo, Wei Zhang, Gang Wei, Xinke Xiao The water entry problem is considered as a classic problem which has a long research history, however, projectile water entry is still a difficult problem that has not been completely solved. In this paper, the effects of the projectile nose shape on laws of velocity attenuations for all projectiles were studied by a series of numerical simulations using the AUTODYN-2D. The projectiles including the hemispherical and ogival projectiles with three CRH (caliber-radius-head) have been set to a constant mass and their water-entry velocities were in the range of 300m/s $\sim $ 1500m/s. The result showed that the drag coefficient increases monotonically with increasing initial velocities for an identical projectile but decrease with the increase of the CRH for ogival projectiles at the same velocity. It was found that the relation between the drag coefficient and the initial velocities for all projectiles can be expressed as a general equation. Correspondingly, the relation between the drag coefficient and the CRH value of ogival projectiles was also presented in this paper. [Preview Abstract] |
Wednesday, June 29, 2011 12:00PM - 12:15PM |
M6.00005: Investigations of RF Emissions from High-Velocity Impacts of Various Metals William Brown, Mark Schmidt, William Broad We describe a series of experiments to examine emissions in the radio-frequency (RF) portion of the electromagnetic spectrum, resulting from high-velocity impacts of various metals. A two-stage gas gun was used to impact aluminum (6061-T6) spheres, at velocities of approximately 6 km/s, against aluminum/titanium alloy (Ti6Al4v) target plates. In most experiments, debris ejected from the rear surfaces of target plates impacted against witness plates of various metals (aluminum, copper, zinc). The witness plates were placed at various distances from rear surfaces of target plates, and electric field probes were used to obtain measurements of three near-field orthogonal components of the electric fields at sampling rates of 10 giga-samples/s. Additionally, we describe a series of finite-difference impact calculations to simulate these experiments, and determine approximate values of material state variables. From experimental and computational results, we have developed a semi-empirical model describing dependence of the electric field amplitude and frequency on material strength and impact conditions. [Preview Abstract] |
Wednesday, June 29, 2011 12:15PM - 12:30PM |
M6.00006: Low-Order Modeling of Micro-Flier Impact with Thin Stationary Targets Mark Fry, Keith Gonthier The impact of high-speed (500-1500~m/s), laser driven micro-fliers with thin energetic targets (10-100~$\mu$m) is being examined to characterize impact-induced heating and combustion of these materials. To guide development of experiments, a low-order (zero-dimensional) model is formulated to estimate ballistic performance for large dimensional parameter spaces in a computationally inexpensive manner. The model accounts in a simple way for both the early time system dynamics associated with wave propagation and the late time dynamics associated with target penetration and perforation. The model is currently being validated against impact data for larger scale flier-target configurations, and is being used to give predictions for micro-scale configurations. Preliminary predictions for the impact of aluminum micro-fliers with thin steel targets indicate that the ballistic behavior is sensitive to micro-flier mass and geometry. The imaging of post-impact target coupons will be used to gain insight into deformation and failure modes, and to enhance model development. [Preview Abstract] |
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